DESCRIPTION(Adapted from applicant's abstract): Lithium is the mainstay treatment for bipolar affective disorder, with 0.1 percent of the population being treated. Understanding lithium's complex mechanisms of action will help reveal causes of mood disorders and development of targeted drugs. This project focuses on specific hypotheses concerning lithium's actions, in conjunction with studies of basic neuronal signaling mechanisms. Also, valproate and carbamazepine are therapeutic for bipolar disorder, so biochemical actions common to lithium and these two drugs would strengthen the link to their therapeutic effects. The prime actions of these drugs appear to alter signaling activities which impact on neural plasticity, encompassing regulation of signals leading to transcription factor activation and to regulation of the cytoskeleton. Specific Aim-1 will test the hypotheses that lithium, valproate, and carbamazopine modulate signaling activities associated with the receptor-coupled phosphoinositide signal transduction system, using muscarinic receptor-expressing human neuroblastoma SH-SY5Y cells as a model system. There are three components to this aim. Component I will test the hypotheses that (a) muscarinic stimulation increases protein tyrosine phosphorylation, including Gq/11, and protein complex formation, (b) tyrosine phosphorylation is necessary for phosphoinositide signaling and activation of AP-1 and Egr-l, (c) these processes are modulated by anti-bipolar drugs. comDonent 2 will test the hypotheses that (a) muscarinic stimulation increases Gq/11 pahnitoylation, (b) pahnitoylation is necessary for optimal signaling, (c) palmitoylation and tyrosine phosphorylation of Gq/11 regulate one another, (d) palmitoylation is modulated by the therapeutic drugs. Component 3 will test the hypotheses that (a) muscarinic stimulation of signaling is modulated by RGS2 (Regulators of G-protein Signaling), (b) association of RGS2 with Gq/11 is regulated by specific mechanisms, (c) RGS2's action is modulated by the therapeutic drugs. Specific Aim 2 will test the hypotheses that lithium causes alterations in neuronal cytoskeletal organization and function through inhibition of glycogen synthase kinase-3p (GSK3~) resulting in decreased tau and MAP-1B phosphorylation and increased ,B-catenin and Tcf/Lef DNA binding in SH-SY5Y cells. There are three components to this aim.Component I will test the hypotheses that (a) lithium site-specifically reduces phosphorylation of tau and MAP-1B, (b) this is evident at therapeutic lithium concentrations, (c) valproate and carbamazepine affect phosphorylation, (d) these drugs alter localization of tau and MAP-1B, (e) and microtubule stability. Component 2 will test the hypotheses that (a) lithium increases p-catenin levels, (b) this increases cadherin binding (mediates cell adhesion), (c) lithium increases p-catenin-dependent Tcf/Lef transcription factor activation, (d) valproate and carbamazepine have similar effects. Component 3 will test the hypotheses that (a) in postmortem human bipolar brain, tau and MAP-1B have increased site-specific phosphorylation and other alterations opposite those in lithium-treated cells, (b) overexpressed GSK3p in SH-SY5Y cells will model the bipolar condition and will demonstrate enhanced effects of lower concentrations of lithiurn.